Group III nitride crystals are used, for example, in the fields of photoelectric devices such as semiconductor lasers, light-emitting diodes, sensors, and the like; heterojunction high-speed electronic devices; and the like. As a method of producing a Group III nitride crystal, the halide vapor phase epitaxy (HVPE method, for example, see Patent Document 1) and the like are in practical use.
However, the HVPE method has a problem of a by-product (e.g., NH4Cl) generated in crystal generation adversely affecting the crystal generation by blocking an exhaust tube of a production apparatus or the like. For solving this problem, a method of producing a Group III nitride crystal in which Group III oxide is caused to react with reducing gas to generate Group III oxide reduced product gas and then the Group III oxide reduced product gas is caused to react with nitrogen-containing gas to generate a Group III nitride crystal has been proposed (see Patent Document 2). In this method, a halogen-containing by-product does not adversely affect crystal generation because the method can be performed without using halide.